Various systems have been developed to test differential signals from a device under test (DUT). There are a variety of ways to connect the test system to the DUT. These may include a soldered connection, RF connector, pressure contacts, wires/leads, pins, adapters, interposers, clip-ons etc. A common interface to connect the test system to the DUT is accomplished by using a pair of pins/short wires that are soldered to the differential test points, which are then connected to the test system via a cable. The problem with such systems is that ambient electric fields may interact with the cable, which may lack sufficient shielding in some cases, causing interference with the signals. Interference with both signals is referred to as common mode interference. The poorly shielded cable may experience both common mode interference and interference affecting the individual wires/leads. There is no mechanism in the cable to isolate the differential signal from the interference occurring across the cable, resulting in added signal noise that is measured by the testing system but is not present in the DUT. As such, a poorly shielded cable reduces the accuracy of test measurements taken by a testing system, particularly when measuring a differential signal with higher frequency content.
Embodiments of the invention address these and other issues in the prior art.